Illinois History

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The area of Illinois was part of the original territory of the United States, being part of lands ceded by four states to the United States and designated in 1787 as the "Territory northwest of the River Ohio." Illinois Territory was organized on February 3, 1809, from the western part of Indiana Territory, and included all of present-day Illinois, most of Wisconsin, the western part of the Upper Peninsula of Michigan, and northeastern Minnesota.

Although the territory had not yet been legally established, census data for Illinois are available beginning with the 1800 census. The 1810 population is for the entire area of the Illinois Territory, including territory not in the present state. For an explanation of the revision to the 1800 population of Illinois, see Richard L. Forstall, Population of States and Counties of the United States: 1790-1990, Washington, DC: U.S. Government Printing Office, 1996, page 48.

Data for the legally established state of Illinois are available beginning with the 1820 census.

County Subdivisions

There are 1,710 county subdivisions in Illinois known as minor civil divisions (MCDs); 85 counties have functioning, but not necessarily active, townships and 17 counties have nonfunctioning election precincts. There are 1,432 townships and 274 election precincts. Chicago city is independent of any MCD and serves as an MCD equivalent in two counties, creating two county subdivisions. There are also two undefined MCDs that cover the Illinois portion of Lake Michigan. Alexander, Calhoun, Edwards, Hardin, Johnson, Massac, Menard, Monroe, Morgan, Perry, Pope, Pulaski, Randolph, Scott, Union, Wabash, and Williamson counties have election precincts. All other counties have townships. The governing body for each township is an elected township supervisor and a board of trustees.

State Legislative Districts

There are 59 state senate districts and 118 state house districts in Illinois. There is also one state house district undefined and one state senate district undefined each comprising the portion of Illinois in Lake Michigan.

Most & Least Diverse Places in America - The Diversity Index (DI) is a scale of 0 to 100 that represents the likelyhood that two persons, chosen at random from the same area, belong to different race or ethnic groups.